What question did this study set out to answer?

To develop high-performance polyimide rigid foams with exceptional mechanical and heat resistance properties.

February 19, 2026Industrial & Engineering Chemistry Research0 citations

Synergistic Cocrosslinking Strategy toward Ultrahigh Heat-Resistant Polyimide Rigid Foams with Integrated Mechanical Strength, Flame Retardancy, and Thermal Insulation

XSXianzhe ShengNorthwestern Polytechnical University SYShuhuan YunNorthwestern Polytechnical University ZXZhenyu XiongNorthwestern Polytechnical University

Key Points

To develop high-performance polyimide rigid foams with exceptional mechanical and heat resistance properties.
Developed a cocross-linking and foaming strategy using norbornene-end-capped cross-linkable blowing agent and maleic anhydride-end-capped PI oligomer.
Fabricated polyimide rigid foams with integrated mechanical strength, flame retardancy, and thermal insulation.
Evaluated properties including compressive strength, thermal degradation temperature, and thermal conductivity.
Achieved compressive strength of 1.9 MPa at room temperature and 1.7 MPa at 200 °C.
Obtained thermal degradation temperature of 500.3 °C and glass transition temperature exceeding 410 °C.
Demonstrated low thermal conductivity of 0.041 W/(m·K) at room temperature and flame retardancy with a LOI exceeding 40%.

Abstract

Lightweight and high-performance polyimide rigid foams (PIRFs), exhibiting outstanding heat resistance and mechanical properties, as well as excellent flame retardancy, are increasingly required for specialized load-bearing applications. However, commercially available polyimide (PI) foams, which are mostly flexible and low-density, are thermally and mechanically inadequate for high load-bearing purposes. Herein, a scalable and high-efficiency “kill two birds with one stone” cocross-linking and foaming strategy is developed for the fabrication of highly heat-resistant, mechanically strong, and flame-retardant cocross-linked polyimide rigid foams (PIRFs) using the norbornene-end-capped cross-linkable blowing agent (NE-CBA) as both cross-linking agent and blowing agent. Benefiting from the simultaneous construction of high-density cocrosslinked networks and tailorable closed-cell structures via the reaction of maleic anhydride-end-capped PI oligomer (ME-PIO) and NE-CBA, the resultant cocrosslinked PIRFs exhibit exceptional heat resistance, with an ultrahigh glass transition temperature ( T g ) of 410.6 °C and a remarkable thermal degradation temperature ( T d ) of 500.3 °C. Moreover, they possess outstanding mechanical properties, with a high compressive strength of 1.9 MPa at room temperature and 1.7 MPa at as high as 200 °C, with a low mass density of 157 kg/m 3 . In addition, the PIRFs exhibit excellent thermal insulation properties, with low thermal conductivities (λ) of 0.041 W/(m·K) at room temperature and 0.057 W/(m·K) even at 200 °C, as well as desirable flame retardancy with a high limiting oxygen index (LOI) exceeding 40%. Owing to the dual functionality of the NE-CBA employed in this strategy and the resulting synergistic effect, the PIRFs achieve the T g > 410 °C and compressive strength exceeding 1.9 MPa at a foam density of 157 kg/m 3 . This represents the successful simultaneous achievement of low density, ultrahigh heat resistance, and high mechanical strength. The highly heat-resistant and mechanically strong cocross-linked PIRFs, with superior thermal insulation and flame-retardant performance, show significant potential in fields such as aerospace engineering, shipbuilding, railway transportation, and other specialized high-temperature applications.

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